docs: def handle_activity_legacy(_: str, __: int, tokens: ParseResults) -> ParseResults:
      """Handle BEL 1.0 activities."""
      legacy_cls = language.activity_labels[tokens[MODIFIER]]
      tokens[MODIFIER] = ACTIVITY
      tokens[EFFECT] = {
          NAME: legacy_cls,
          NAMESPACE: BEL_DEFAULT_NAMESPACE
      }
      log.log(5, 'upgraded legacy activity to %s', legacy_cls)
      return tokens